Fixed bug 4369 - Going fullscreen with green knob in MacOS freezes app for 15 seconds.

Elmar

creating a fullscreen window with SDL_CreateWindow(..SDL_WINDOW_FULLSCREEN_DESKTOP..) in MacOS works fine, except if it was triggered by the user with the green knob in the top left window title bar.

Then "something" is different, and SDL_CreateWindow hangs for 15-20 seconds (tested in MacOS 10.13 and 10.14).

Responsible for the hang is this code in SDL_cocoawindow.m - Cocoa_SetWindowFullscreenSpace:

        const int maxattempts = 3;
        int attempt = 0;
        while (++attempt <= maxattempts) {
            /* Wait for the transition to complete, so application changes
             take effect properly (e.g. setting the window size, etc.)
             */
            const int limit = 10000;
            int count = 0;
            while ([data->listener isInFullscreenSpaceTransition]) {
                if ( ++count == limit ) {
                    /* Uh oh, transition isn't completing. Should we assert? */
                    break;
                }
                SDL_Delay(1);
                SDL_PumpEvents();
            }
            if ([data->listener isInFullscreenSpace] == (state ? YES : NO))
                break;
            /* Try again, the last attempt was interrupted by user gestures */
            if (![data->listener setFullscreenSpace:(state ? YES : NO)])
                break; /* ??? */
        }

One trivial workaround is to change 'const int limit = 10000' to 500. Then the freeze is so short that it doesn't look like a freeze to the user.

Looking further into the problem, I observed that the function Cocoa_SetWindowFullscreenSpace recursively calls itself via some ObjectiveC messages. I managed to extract a callstack for this (copied below): Note how Cocoa_SetWindowFullscreenSpace in stack line 22 calls SDL_PumpEvents, which eventually arrives at  SDL_SendWindowEvent, which calls SDL_UpdateFullscreenMode (stack line 0), which then calls Cocoa_SetWindowFullscreenSpace again (not shown). This recursive second call is the one that hangs.

Another "solution" that worked for me was to add a flag to SDL_Window that is set in Cocoa_SetWindowFullscreenSpace and causes this function to return immediately if called from itself.

Obviously, this is also an ugly hack, but I don't have enough time to dive into this crazy Cocoa/ObjectiveC business deep enough to find a proper solution. But hopefully it's easy for one of the experts around.

Note that there is a "failure to go fullscreen"-message involved, maybe using the green knob causes this failure at first.

I can unfortunately not provide a minimum example.

Best regards,
Elmar

0   com.yasara.View               	0x00000001007495af SDL_UpdateFullscreenMode + 207
1   com.yasara.View               	0x00000001006e2591 SDL_SendWindowEvent + 401
2   com.yasara.View               	0x0000000100775a72 -[Cocoa_WindowListener windowDidResize:] + 370
3   com.yasara.View               	0x0000000100776550 -[Cocoa_WindowListener windowDidExitFullScreen:] + 512
4   com.apple.AppKit              	0x00007fff3180a2a4 -[_NSWindowEnterFullScreenTransitionController failedToEnterFullScreen] + 692
5   com.apple.AppKit              	0x00007fff31c59737 -[_NSEnterFullScreenTransitionController _doFailedToEnterFullScreen] + 349
6   com.apple.AppKit              	0x00007fff3172aa53 __NSFullScreenDockConnectionSendEnterForSpace_block_invoke + 135
7   libxpc.dylib                  	0x00007fff6114b9b1 _xpc_connection_reply_callout + 36
8   libxpc.dylib                  	0x00007fff6114b938 _xpc_connection_call_reply_async + 82
9   libdispatch.dylib             	0x00007fff60ec7e39 _dispatch_client_callout3 + 8
10  libdispatch.dylib             	0x00007fff60ede3b0 _dispatch_mach_msg_async_reply_invoke + 322
11  libdispatch.dylib             	0x00007fff60ed2e25 _dispatch_main_queue_callback_4CF + 807
12  com.apple.CoreFoundation      	0x00007fff33d39e8b __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
13  com.apple.CoreFoundation      	0x00007fff33d3959a __CFRunLoopRun + 2335
14  com.apple.CoreFoundation      	0x00007fff33d38a28 CFRunLoopRunSpecific + 463
15  com.apple.HIToolbox           	0x00007fff32fd1b35 RunCurrentEventLoopInMode + 293
16  com.apple.HIToolbox           	0x00007fff32fd1774 ReceiveNextEventCommon + 371
17  com.apple.HIToolbox           	0x00007fff32fd15e8 _BlockUntilNextEventMatchingListInModeWithFilter + 64
18  com.apple.AppKit              	0x00007fff3128deb7 _DPSNextEvent + 997
19  com.apple.AppKit              	0x00007fff3128cc56 -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1362
20  com.yasara.View               	0x000000010076fab2 Cocoa_PumpEvents + 290
21  com.yasara.View               	0x00000001006dd1c7 SDL_PumpEvents_REAL + 23
22  com.yasara.View               	0x00000001007795cf Cocoa_SetWindowFullscreenSpace + 223
23  com.yasara.View               	0x000000010074970b SDL_UpdateFullscreenMode + 555
24  com.yasara.View               	0x00000001006e2476 SDL_SendWindowEvent + 118
25  com.yasara.View               	0x0000000100774ff7 -[Cocoa_WindowListener resumeVisibleObservation] + 135
26  com.yasara.View               	0x000000010077664c Cocoa_ShowWindow + 188
27  com.yasara.View               	0x0000000100749492 SDL_FinishWindowCreation + 546
28  com.yasara.View               	0x0000000100748da5 SDL_CreateWindow_REAL + 1573
29  com.yasara.View               	0x000000010010d9b1 vga_setvideomode + 1347
30  com.yasara.View               	0x00000001003f0d46 mod_initscreen + 2614
31  com.yasara.View               	0x00000001003f344b mod_reinitscreen + 460
32  com.yasara.View               	0x00000001003f370d mod_resizescreen + 383
33  com.yasara.View               	0x0000000100418e39 mod_main + 815
34  com.yasara.View               	0x000000010029ca5d main2 + 5766
35  com.yasara.View               	0x000000010011d1b7 main.main_cpuok + 19

src/video/cocoa/SDL_cocoawindow.h

@@ -116,7 +116,7 @@ struct SDL_WindowData
     NSView *sdlContentView; /* nil if window is created via CreateWindowFrom */
     NSMutableArray *nscontexts;
     SDL_bool created;
-    SDL_bool inWindowMove;
+    SDL_bool inWindowFullscreenTransition;
     Cocoa_WindowListener *listener;
     struct SDL_VideoData *videodata;
 #if SDL_VIDEO_OPENGL_EGL

src/video/cocoa/SDL_cocoawindow.m

@@ -2030,6 +2030,11 @@ Cocoa_SetWindowFullscreenSpace(SDL_Window * window, SDL_bool state)
     SDL_bool succeeded = SDL_FALSE;
     SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
 
+	if (data->inWindowFullscreenTransition) {
+		return SDL_FALSE;
+	}
+
+	data->inWindowFullscreenTransition = SDL_TRUE;
     if ([data->listener setFullscreenSpace:(state ? YES : NO)]) {
         const int maxattempts = 3;
         int attempt = 0;
@@ -2056,6 +2061,7 @@ Cocoa_SetWindowFullscreenSpace(SDL_Window * window, SDL_bool state)
         /* Return TRUE to prevent non-space fullscreen logic from running */
         succeeded = SDL_TRUE;
     }
+	data->inWindowFullscreenTransition = SDL_FALSE;
 
     return succeeded;
 }}